De-energized tap changer for transformers with polyphase sliding contact assembly

ABSTRACT

A de-energized tap changer for transformers comprises a frame of insulating material, a slide which carries movable contacts, the slide being displaceable in the frame, and a drive for the slide. The frame of the tap changer is manufactured in one piece and consists of a terminal bar with attachment means for connections from the transformer windings, a carrier member carrying the drive, and cross-bars connecting the terminal bar and the carrier member. The movable slide is displaceable in grooves in the cross-bars and can be inserted in the grooves only when situated outside its ordinary working area.

United States Patent 1191 Norman et a1.

[75] Inventors: Sivert Norman; Jan Syren, Uno

Zetterlund, all of Ludvika, Sweden [73] Assignee: Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden [22] Filed: June 5, 1973 [21] Appl. No.: 367,098

[30] Foreign Application Priority Data June 27, 1972 Sweden 8402/72 [52] us. (:1 200/16 F, 200/17 11,200/16 c 51 1111.01. ..u0111 15/06 [58] Field 61 Search 200/11 B, 11 TW, 16 B, 200/16 E, 16 F, 17 R, 11 TC, 18,156, 162,

[56] References Cited UNITED STATES PATENTS 2,502,438 4/1950 Deakin 200/16 F X 2,577,955 12/1951 Dixon 200/16 F X 1 July 16, 1974 Foley et al 200/11 B UX 3,045,090 7/1962 Wilson, Jr. et al. 200/11 B X 3,192,328 6/1965 Wilson, Jr. 200/11 B 3,639,706 2/1972 Purdy 200/16 F X 3,673,364 6/1972 Klein 200/16 F X FOREIGN PATENTS OR APPLICATIONS 950,794 10/1956 Germany 139,352 3/1953 Sweden Primary Examiner-James R. Scott 57 ABSTRACT A tie-energized tap changer for transformers comprises a frame of insulating material, a slide which carries movable contacts, the slide being displaceable in the frame, and a drive for the slide. The frame of the tap changer is manufactured in one piece and consists of a terminal "bar with attachment means for connections from the transformer windings, a carrier member carrying the drive, and cross-bars connecting the terminal bar and the carrier member. The movable slide is displaceable in grooves in the cross-bars and can be inserted in the grooves only when situated outside its ordinary working area.

7 Claims, 4 Drawing Figures PATENTEDJUL 1 6 I974 sum '1 (IF 2 DE-ENERGIZED TAP CHANGER FOR TRANSFORMERS WITH POLYPHASE SLIDING CONTACT ASSEMBLY BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION The present inventionrelates' to a de-energized tap changer for transformers and comprises a frame of in- I sulating material, a slide having movable contacts, said slide being displaceable in the frame, and drive means for the slide. According to the invention the frame, manufactured in one piece, comprises a terminal bar with attachment means for connections from the transformer windings, a carrier member supported by crossbars from the drive means and grooves arranged in the cross-bars for the movable slide.

Because the frame is manufactured in one piece and constructed as described hereinafter, the job of assembling the de-energized tap changer is considerably simplified in comparison with the types of tap changers now in use. Furthermore, the tap changer can be modified so that it can be used both for linear and zig-zag connection ofthe control winding and for Y or D connection of the transformer.

Essentially, the tap changer includes a frame of insulating material which has cross-bars and a carrier member forming parts of the frame, the cross-bars supporting the carrier member at a distance from the terminal bar. A slide with contacts thereon is displaceably mounted in the frame for engagement with connections from the transformer windings. The contacts on the slide have contact surfaces, one contact surface being of a length less than the distance between two adjacent stationary contacts while the other contact surface is at least as long as a distance between two stationary contacts. The contactsmounted on the slide can be turned upside down for zig-zag connection.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings FIG. I shows the deenergized tap changer assembled for linear connection and with connection means for only one phase. FIG. 2 shows a side view of the slide. FIG. 3 is a section along the line lll-Ill in FIG. I and shows a cross-section through a movable contact on the slide. FIG. 4 is a section along the line IV-IV in FIG. I to show how the slide is fitted in a cross-bar.

DESCRIPTION OF THE PREFERRED EMBODIMENTS fully inserted, as can be seen in FIG. 1, thus forming the stationary contacts of the tap changer. Each pin has a peripheral groove 8 and, when the pin is fully inserted in the tube, the sleeve is pressed into the groove so that the pin and sleeve are joined together and the pin is securely anchored in the frame.

In a preferred embodiment of the invention the pins are made of aluminium. This is particularly suitable if the transformer winding is also of aluminium since contact pressure between conductor and pin then permits a reliable connection to be achieved very quickly. The pin 3 is designed partially in the form of a socket into which the transformer-conductor 4 is inserted and the socket is pressed around the conductor in known manner. The free end of the pin, which projects out of the tube is silver-plated in order to give the best possible current-transmitting properties between the pin and the movable contact.

The slide 9 is displaceable in the two cross-bars 6 and has three movable contacts 10, one for each phase. The construction of the contacts can be seen best in FIG. 3 which is a section along the line IIIIII in FIG. 1. Each contact is attached in the slide with the help of two lugs 11 which may be moulded in one piece with the slide or attached to theslide in some known manner. The contact consists of two parallel-trapezoidal contact piecesl2, kept in place between the lugs with the help of two guide pins 13 passing through the contact pieces and nonrotatably mounted in the lugs. The contact pieces are kept at the correct distance from each other by a spacer l4 and pressed against this spacer by two compression springs 15 which abut the contact piece with-one end and are arranged in a groove 16 on each of the. lugs 11 at the other end. Each contact piece has on one flat surface two raised contact surfaces 17 and 18, respectively, one of which, 17, is located in the vicinity of the shorter of thetwo parallel edges of the contact piece while the other contact surface, 18, is located in the vicinity of the long, parallel edge of the piece. FIG. I shows that the short contact surface is in contact with one of the contact pins 3. The length of the short contact surface should be less than the free distance between two adjacent stationary contacts so that it can never connect two such contacts together. The length of the contact surface 18 should be at least I as long as the distance between the centers of two adjacent stationary contacts so that it can connect two adja cent stationary contacts together.

When the contact piece 12 is in the position shown in FIGS. 1 and 3, the fourth stationary contact from the right is joined to a busbar 19 which in turn is connected to a terminal pin 20 furthest to the left in the group of contact pins in the terminal bar. The short contact surface I7 is then in contact with the stationary contact and the long contact surface 18 is in contact with the busbar 19. The three terminal pins 20, one for each phase, are connected in known manner to earth or to a zero point. How this is done is immaterial for an understanding of the invention. The busbar 19, one for each phase, is attached by one end to the terminal pin 20 and by the other end to the frame. ln'FIG. l the bar is assumed to be a tub, its righthand end being pushed over a pin 21. For the lefthand and center bar, the pins are placed on the cross-pieces 6 whereas the support pin for the righthand bar is on a lug 22 on the frame.

According to the embodiment of the invention shown in FIG. 1, the de-energized tap changer is assembled for linear connection, but it can easily be converted for use with zig-zag connections. In such a connection the transformer control winding is divided into two parts and the connections from the two parts are connected alternately to the pins 3. Two adjacent pins or stationary contacts are then permanently connected together by the movable contact 10. With this connection no busbar is necessary and the terminal pin may be replaced by a pin 3 if necessary. In order to be able to connect two stationary contacts, the two contact pieces 12 are turned upside down so that the long contact surface 18 abuts the stationary contacts. The short contact The de-energized tap changer is assembled as follows:

Theslide, together with its three movable contacts, is placed over the grooves in the frame with the recesses above the guide-bosses 24. In this position the slide can be placed in the grooves. The slide is then moved to one side, to the right in the embodiment shown in FIG. 1, so that the recesses 29 are opposite the position of the toothed wheel. The toothed wheel is then positioned with its teeth engaging the recesses. The shaft 27 which transfers the driving movement to the toothed wheel is inserted and locked in position so that the toothed wheel cannot be moved from its plane.

. contacts thereon for connection with the transformer windings and engageable by said movable contacts,

4 said mounting means comprising cross-bars (6) forming a part of the frame and extending transversely to the direction of movement of the slide and having grooves (23) therein for mounting the movable slide (9), and a carrier member forming a part of the frame and supported by the cross-bars at a distance from the terminal bar and supporting the drive means for the slide.

2. De-energized tap changer according to claim 1, in which each cross-bar (6) is'provided with a guide boss (24) projecting slightly over the groove (23) for the 24 which protrudes slightly across the groove. This can be seen best in FIG. 4. The slide is thus normally locked in the grooves. So that the slide can be put in position in the grooves, it is provided with two recesses 25, the distance between these being equal to the distance between the guide bosses 24. When the slide is placed over the grooves 23 with the recesses 25 opposite the guide bosses24, the slide can be moved into place in the groove, but as soon as the slide is then moved in one direction or the other, it becomes locked in position by the bosses. The recesses 25 are so positioned that they cannot be located opposite a guide boss during the nor- 'mal operating movements of the tap changer. The

guide boss 24 may be at the side of the groove as shown in FIG. 1 orit maybe placed differently, for example above the groove.

The movement of the slide is effected with the help ofa toothed wheel 26. The, wheel is driven with the help of some known device, not shown here. The toothed wheel is non-rotatably joined to a shaft 27 passing through a lug 28 at one end of the carrier member 5. The carrier arm is preferably provided with a journalling lug at each end so that the toothed wheel can be positioned either to the right or the left depending on the position of the tap changer in the transformer.

The toothed wheel cooperates with recesses 29 on the side of the slide facing the toothed wheel. As can be seen from FIG. 2, the recesses 29 terminate a little way from the upper and lower surfaces of the slide. This means that when the slide is in position in its grooves 23 and the toothed wheel is placed with its teeth in the recesses of the slide; the wheel cannot be moved in the direction of the axis of shaft 27.

slide and the slide is provided with-recesses (25) corresponding'to the guide bosses so that the slide can be placed in the groove when the recesses are opposite the guide bosses and that, after longitudinal displacement, it is held in the groove by the guide bosses.

3. De-energized tap changer according to claim 1, in which the drive means for the slide (9) comprises a toothed wheel (26) journalled in the carrier member '(5), said slide having recesses (29) therein, said wheel engaging in said recesses.

4. De-energized tap changer according to claim 3, in

i which the recesses (29) in the slide corresponding to the teeth in the toothed wheel (26) terminate at a distance from both side surfaces of the slide.

5. De-energized tap changer according to claim 1, in which the slide is provided with three which carry the movable contacts (10).

6. De-energized tap changer according to claim 1, in I which the movable contacts (10) are composed of-two similar contact plates 12) having the shape of a parallel-trapezium, with contact surfaces (17,18) at the parallel edges, one contact surface (17) being shorter than the free distance between adjacent stationary contacts (3) on the terminal plate while the other contact surface (18) is at least as long as the distance between the centers of two adjacent stationary contacts. I

7. A de-energized tap changer according to claim 1, in which the frame is provided with a bus bar (19) for each phase arranged parallel with and at a distance from the terminal bar, and said movable contacts (10) on the slide are reversible and assymme'trical, each contact in each of its positions effecting electrical contact between a single stationary contact and said bus bar and in another position effecting connection pairs of lugs 11) 

1. De-energized tap changer for transformers, comprising a frame of insulating material, a slide having one movable contact for each phase, means mounting said slide displaceably in the frame, and drive means for the slide, in which the frame (1) is manufactured in one piece and comprises a terminal bar (2) with stationary contacts thereon for connection with the transformer windings and engageable by said movable contacts, said mounting means comprising cross-bars (6) forming a part of the frame and extending transversely to the direction of movement of the slide and having grooves (23) therein for mounting the movable slide (9), and a carrier member forming a part of the frame and supported by the cross-bars at a distance from the terminal bar and supporting the drive means for the slide.
 2. De-energized tap changer according to claim 1, in which each cross-bar (6) is provided with a guide boss (24) projecting slightly over the groove (23) for the slide and the slide is provided with recesses (25) corresponding to the guide bosses so that the slide can be placed in the groove when the recesses are opposite the guide bosses and that, after longitudinal displacement, it is held in the groove by the guide bosses.
 3. De-energized tap changer according to claim 1, in which the drive means for the slide (9) comprises a toothed wheel (26) journalled in the carrier member (5), said slide having recesses (29) therein, said wheel engaging in said recesses.
 4. De-energized tap changer according to claim 3, in which the recesses (29) in the slide corresponding to the teeth in the toothed wheel (26) terminate at a distance from both side surfaces of the slide.
 5. De-energized tap changer according to claim 1, in which the slide is provided with three pairs of lugs (11) which carry the movable contacts (10).
 6. De-energized tap changer according to claim 1, in which the movable contacts (10) are composed of two similar contact plates (12) having the shape of a parallel-trapezium, with contact surfaces (17,18) at the parallel edges, one contact surface (17) being shorter than the free distance between adjacent stationary contacts (3) on the terminal plate while the other contact surface (18) is at least as long as the distance between the centers of two adjacent stationary contacts.
 7. A de-energized tap changer according to claim 1, in which the frame is provided with a bus bar (19) for each phase arranged parallel with and at a distance from the terminal bar, and said movable contacts (10) on the slide are reversible and assymmetrical, each contact in each of its positions effecting electrical contact between a single stationary contact and said bus bar and in another position effecting connection between adjacent stationary contacts. 